The need for splints or artificial ligaments to replace or supplement natural ligaments and tendons where such ligaments and tendons have suffered damage, usually accidental, is sufficiently widespread so that conferences have been held on the subject and the problem has been discussed in reports by orthopedic surgeons. An example of a frequently-occurring injury requiring a device of this kind for satisfactory surgical repair is an acromioclavicular dislocation, in which the injury is produced by falling on the point of the shoulder with the arm in the adducted position. By this action one or more of the ligaments confining the acromioclavicular joint may become ruptured, and surfical repair utilizing an appropriate splinting device, to provide internal support for the damaged ligaments, is frequently indicated. Other ligaments such as the medial collateral and anterior cruciate may be similarly repaired.
These constructions may also be useful in surgical reconstruction of damaged tendons including achilles and patellar tendons, and possibly flexor digital tendons. Tendons possess a very poor capacity for self-regeneration, and thus require very long periods of time to effect their own repair without the assistance of a prosthetic implant.
Surgeons who are experienced in the repair of ligament and tendon damage have recommended several desirable characteristics for materials (or constructions) to be applied as internal splints:
(1) The material must be capable of exerting mechanical strength equal to that of the damaged ligament, at least under moderate stress activity.
(2) It must have sufficient resistance to elongation under stress that it will retain its mechanical effectiveness.
(3) The material should be acceptable for permanent implant in the human body, preferably without the necessity for removal by a second operation. An important condition for good acceptability is that the material be sufficiently porous so as to permit invasion by the host tissues.
(4) The splint should permit early activity.
Primarily on account of their desirable characteristics of strength, porosity, and flexibility, the attention of surgeons was directed to woven and knitted Dacron (polyethylene terephthalate, Du Pont) tubular constructions used in vascular surgery as potential materials of construction for ligament splints. However, it has been found that Dacron prosthesis in the constructions conventionally used have inadequate resistance to elongation under stress, the elongation reaching values as high as 150%. Further, it is highly desirable that the cross-section of the prosthesis be such that it will be invaded by the host tissue and that an encasement be provided for formation of a living structure which will supplement the prosthesis.
As is evident, then, a structure which provides for greater resistance to elongation and which is sufficiently rigid so that a tubular structure with an open lumen can be provided is highly to be desired.